Method and system for detecting atomic transition in cold atom microwave clock

Abstract

The invention discloses a method and system for detecting atomic transition in a cold atom microwave clock. The method comprises the steps that an upper energy state signal # imgabs0 # 1 and a lower energy state signal # imgabs1 # 2 of atoms in the cold atom microwave clock are measured in a time-sharing mode through a single photoelectric detector; and according to the upper energy state signal # imgabs2 # 1 and the lower energy state signal # imgabs3 # 2, the atomic transition probability # imgabs4 # is obtained. The problems of large size, high cost and complex calibration caused by the fact that a traditional cold atom microwave clock needs two independent photoelectric detectors to monitor upper / lower energy state atoms respectively are solved, an existing cold atom detection module or technology is simplified, and the miniaturization capacity and level of the cold atom microwave clock are improved.

Description

Technical Field

[0001] The present application belongs to the technical field of atomic frequency standards, and specifically relates to a method and system for detecting atomic transitions in a cold atomic microwave clock. Background Art

[0002] The frequency standard signal output by the cold atom microwave clock has high accuracy and long-term frequency stability, and plays an important role in the fields of timekeeping, satellite navigation and positioning, time and frequency comparison, and precision measurement. The current cutting-edge technological development is the miniaturization and engineering of cold atom microwave clocks. This requires the simplification of the detection method or device for the quantum state of cold atoms; using a single photodetector instead of the traditional dual photodetector is an important direction of simplification. In addition, the laser along the direction of movement of the atomic cluster is used as cooling light during the cooling sequence and as detection light and detection re-pump light during the detection sequence, which can also simplify the optical path. Currently, a single photodetector is used to detect the quantum state of the cold atom, and the transition probability of the atom under the detection of the single photodetector is obtained. , change the microwave frequency f used to stimulate atomic energy level transitions, and measure the corresponding atomic transition probabilities at different frequencies (f); When f is close to the atomic intrinsic transition frequency f0, the transition probability will increase, forming a resonance curve; by finding the frequency point f that makes the transition probability reach the maximum value max The local oscillator is multiplied and synthesized to obtain the clock transition microwave frequency at f max , it can output a frequency standard signal related to the atomic intrinsic transition frequency f0. However, under the condition of a single photodetector, and with only the detection light coinciding with the direction of the atomic motion trajectory, there is no method to obtain the normalized atomic transition probability in a cold atom microwave clock. Summary of the Invention

[0003] In order to address the deficiencies in the prior art, the present application proposes a method and system for detecting atomic transitions in a cold atom microwave clock.

[0004] First, a method for detecting atomic transitions in a cold atomic microwave clock is proposed, including:

[0005] Time-sharing measurement of the upper energy state signal of atoms in a cold atomic microwave clock using a single photodetector 1 and lower energy state signals 2;

[0006] According to the upper energy state signal 1 and lower energy state signals 2. Obtain the atomic transition probability .

[0007] Optionally, the single photodetector is used to time-share measure the upper energy state signal of the atoms in the cold atomic microwave clock. 1 and the lower energy state signal 2, including:

[0008] When the atom passes through the single photodetector, first turn on the probe light and keep it on for the first preset time period T0 and then turn it off. During the time period T0, use the single photodetector to measure the upper energy state signal of the atom in the cold atom microwave clock. 1; then turn on the probe repump light and keep it on for the second preset time period T1 and then turn it off. During the time period T1, pump the atoms in the lower energy state to the upper energy state; finally, turn on the probe light again and keep it on for the third preset time period T2 and then turn it off. During the time period T2, use the single photodetector to measure the lower energy state signal of the atom in the cold atom microwave clock. 2.

[0009] Optionally, the atomic transition probability obtained according to the upper energy state signal 1 and the lower energy state signal 2 is calculated by using the following calculation formula:

[0010]

[0011] where is the first constant coefficient, is the second constant coefficient.

[0012] In a second aspect, an atomic transition detection system in a cold atom microwave clock is proposed, which is used to implement the atomic transition detection method in the cold atom microwave clock described in the first aspect, including:

[0013] An atomic fluorescence acquisition device, which is used to collect the fluorescence emitted when the cold atom is detected by the detection beam and output an electrical signal;

[0014] A signal analysis module, which is used to separate the electrical signal output by the atomic fluorescence acquisition device into the upper energy state signal 1 and the lower energy state signal 2;

[0015] A transition probability calculation module, which is used to calculate the transition probability according to the upper energy state signal 1 and the lower energy state signal 2 output by the signal analysis module .

[0016] Optionally, it further includes:

[0017] A timing control module, which is used to turn on the probe light for the first step of detection for the first preset time period, turn on the probe repump light for atomic state pumping for the second preset time period, and turn on the probe light for the second step of detection for the third preset time period.

[0018] ​Optionally, the atomic fluorescence collection device consists of a central lens, single photodetectors arranged on both sides of the lens, and a cold atom cluster motion region in a vacuum system; wherein the cold atom cluster motion region emits fluorescence when receiving detection light and detecting heavy pump light.

[0019] In a third aspect, an electronic device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the method for detecting atomic transitions in a cold atom microwave clock in the first aspect are implemented.

[0020] In a fourth aspect, a computer storage medium is provided, on which a computer program is stored, which, when executed by a processor, implements the steps of the method for detecting atomic transitions in a cold atomic microwave clock in the first aspect.

[0021] In a fifth aspect, a computer program product is provided, comprising a computer program or instructions, which, when executed by a processor, implement the steps of the method for detecting atomic transitions in a cold atom microwave clock in the first aspect.

[0022] The beneficial effects of the technical solutions provided by some embodiments of the present application include at least:

[0023] The present application provides a method and system for detecting atomic transitions in a cold atom microwave clock, wherein the method comprises using a single photodetector to time-share the upper energy state signal of atoms in the cold atom microwave clock. 1 and lower energy state signals 2. According to the upper energy state signal 1 and lower energy state signals 2. Obtain the atomic transition probability This application solves the problems of large size, high cost and complex calibration caused by the need for two independent photodetectors to monitor the upper and lower energy state atoms respectively in traditional cold atom microwave clocks. It simplifies the existing detection modules or technologies of cold atoms and improves the miniaturization capability and level of cold atom microwave clocks.

[0024] Other features and advantages of the present application will be described in the following description, and in part will become apparent from the description or be understood by practicing the present application. The objectives and other advantages of the present application are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0025] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings.

[0026] Advantages of additional aspects of the present application will be given in part in the following description, and in part will become apparent from the following description, or will be learned through practice of the present application. Brief Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments of the present application or the prior art. Obviously, the following described drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 It is a flow chart of the method for detecting atomic transitions in the cold atom microwave clock shown in the embodiments of the present application;

[0029] Figure 2 It is a schematic diagram of the working principle of the atomic fluorescence acquisition device shown in the embodiments of the present application;

[0030] Figure 3 It is a schematic diagram of the upper energy state signal and the lower energy state signal of atoms in the cold atom microwave clock at the computer end shown in the embodiments of the present application;

[0031] Figure 4 It is a graph showing the change of the atomic transition probability with the fed microwave frequency in the cold atom microwave clock at the computer end shown in the embodiments of the present application;

[0032] Figure 5 It is a schematic block diagram of the principle of the atomic transition detection system in the cold atom microwave clock shown in the embodiments of the present application.

[0033] Wherein, 1 - single photodetector, 2 - lens, 3 - moving area of the cold atom cloud, 4 - instantaneous position of the cold atom cloud. Detailed Embodiments

[0034] To make the objectives, technical solutions and advantages of the present application clearer, the following will further describe the embodiments of the present application in detail with reference to the drawings.

[0035] When the following description involves the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are only examples of methods and devices consistent with some aspects of the present application as detailed in the appended claims.

[0036] In the description of this application, it should be understood that the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances. In addition, in the description of this application, unless otherwise specified, "multiple" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the previous and subsequent associated objects are in an "or" relationship.

[0037] Example 1

[0038] The following will be combined with the Figure 1 , a method for detecting atomic transitions in a cold atom microwave clock provided in an embodiment of the present application is introduced in detail.

[0039] A method for detecting atomic transitions in a cold atomic microwave clock comprises the following steps:

[0040] Step S1: Use a single photodetector to measure the upper energy state signal of the atoms in the cold atomic microwave clock in a time-sharing manner 1 and lower energy state signals 2;

[0041] Specifically, when an atom passes through a single photodetector, the detection light is first turned on and lasts for a first preset time period T0 and then turned off. During the T0 time, the single photodetector is used to measure the upper energy state signal of the atom in the cold atomic microwave clock. 1; then turn on the detection heavy pump light and continue for the second preset time period T1, then turn it off. During T1, the atoms in the lower energy state are pumped to the upper energy state; finally, turn on the detection light again and continue for the third preset time period T2, then turn it off. During T2, a single photodetector is used to measure the lower energy state signal of the atoms in the cold atomic microwave clock. 2. Usually, the probe light and the probe re-pump light are generated by a semiconductor laser locked to the atomic energy level transition line.

[0042] Step S2: According to the upper energy state signal 1 and lower energy state signals 2. Obtain the atomic transition probability .

[0043] During the detection phase of the cold atom microwave clock, atoms are in two hyperfine sub-states of the ground state. The two sub-energy levels are called the upper energy state and the lower energy state according to their energy levels. The ratio of the number of atoms in the lower energy state to the total number of atoms is called the transition probability.

[0044] Specifically in this embodiment, in step S1, the probe light is first turned on and then turned off after a first preset time period T0, and the detection within the first preset time period T0 is regarded as the first detection step. Only the atoms in the upper energy state emit fluorescence. After the fluorescence electrical signal is collected by the computer, the upper energy state signal is output. 1. For a specific example Figure 3 As shown by the shaded area on the left, it represents the value proportional to the number of atoms in the upper energy state obtained by accumulating the voltage value in the window function and subtracting the background value. The value below the dashed line is the background value, and the same applies hereinafter; during the acquisition in this step, the atoms in the upper energy state will disperse and some will be lost.

[0045] The probe repump light is turned on and then turned off after a second preset time period T1. During the second preset time period T1, the atoms in the lower energy state are converted into atoms in the upper energy state under the action of the probe repump light.

[0046] The probe light is turned on again and then turned off after a third preset time period T2, and the detection within the third preset time period T2 is regarded as the second detection step. During the second detection step, the atoms converted into the upper energy state under the action of the probe repump light and the atoms in the upper energy state that have not been lost after the first detection emit fluorescence together. After the fluorescence signal is collected by the computer, the lower energy state signal is output. 2. For a specific example Figure 3 As shown by the shaded area on the right, it represents the value proportional to the sum of the number of atoms in the lower energy state and the number of atoms in the upper energy state that have not been lost obtained by accumulating the voltage value in the window function and subtracting the background value.

[0047] During the specific implementation process, the number of atoms in the upper energy state is denoted as , and the number of atoms in the lower energy state is denoted as ,

[0048] The above physical parameters satisfy: ,

[0049] ;

[0050] Among them, , , are three constant coefficients;

[0051] During the specific implementation process, is the value after processing the fluorescence electrical signal ( =1, 2) is the proportionality coefficient between the number of atoms emitting fluorescence. This value is cancelled out in the final result and does not appear; is the ratio of the detection efficiency of the detector formed by the different positions of the cold atom cloud during the two detections. This value is near 1; is the proportion value of the atoms in the upper energy state remaining in the cold atom cloud after the first detection. This value is generally between 0 and 0.5.

[0052] From the calculation relationships of the above physical variables, it can be obtained that: according to the upper energy state signal 1 and the lower energy state signal 2, the expression for calculating the atomic transition probability is:

[0053]

[0054] In the specific implementation process, it is necessary to adjust according to the experimental results of scanning the transition probability , two parameters, so that the transition probability is between 0 and 1, and the value fluctuates minimally.

[0055] Experimental result test

[0056] The cooled atoms will undergo Ramsey transitions in the excitation microwave cavity. By scanning the microwave frequency in the microwave cavity, the detected and calculated transition probability will show Ramsey fringe patterns, as Figure 4 shown. Adjust , two parameters, so that the transition probability forms a distinct fringe pattern between 0 and 1; at this time, find the average value μ and the standard deviation σ of , and make the value of σ / μ the smallest. At this time, it is the , optimal value of

[0057] This method can be used as a general practice for obtaining the atomic probability of a cold atom microwave clock under the condition of a single photodetector.

[0058] By using a single photodetector in this application to detect the quantum state of cold atoms at different times, a photoelectric signal is obtained. Then, by detecting the ratio of the number of atoms in the lower energy state to the total number of atoms, the transition probability of the atoms under the detection of this single photodetector is obtained. This method solves the problems of large volume, high cost, and complex calibration caused by the need for two independent photodetectors to monitor the upper / lower energy state atoms in traditional cold atom microwave clocks, simplifies the existing detection module or technology of cold atoms, and improves the miniaturization ability and level of cold atom microwave clocks.

[0059] Embodiment 2

[0060] This application proposes an atomic transition detection system in a cold atom microwave clock for implementing the atomic transition detection method in the cold atom microwave clock described in Embodiment 1, including:

[0061] An atomic fluorescence acquisition device is used to collect the fluorescence emitted when cold atoms are detected by a detection beam and output an electrical signal;

[0062] In the specific implementation process, the atomic fluorescence acquisition device is as Figure 2 shown, and is composed of a lens 2 in the center, a single photodetector 1 respectively arranged on both sides of the lens 2, and a cold atom group movement area 3 (i.e., the beam positions of the detection light and the detection heavy pump light) located in the vacuum system; 4 is the instantaneous position of the cold atom group; the receiving surface of the single photodetector 1 is perpendicular to the axis direction of the lens 2, and the principle process is as follows: the detection beam irradiates the cold atom group at the instantaneous position 4 of the cold atom group, and the cold atoms will emit fluorescence; the fluorescence is collected by the lens 2 and focused on the photodetector, and the single photodetector 1 generates an electrical signal, which is processed, and the computer collects the fluorescence intensity signal. Specifically, the detection beam includes two different frequencies of lasers, the detection light and the detection heavy pump light; the detection light irradiates the cold atom group, which can cause the upper energy state atoms in the cold atom group to emit fluorescence, and the lower energy state atoms do not emit fluorescence; the detection heavy pump light can convert the lower energy state into upper energy state atoms;

[0063] A signal analysis module is used to separate the electrical signal output by the atomic fluorescence acquisition device into an upper energy state signal 1 and a lower energy state signal 2;

[0064] A transition probability calculation module is used to calculate the transition probability according to the upper energy state signal 1 and the lower energy state signal 2 output by the signal analysis module ;

[0065] In a feasible implementation manner, as Figure 5 shown, it further includes:

[0066] A timing control module is used to turn on the detection light for the first step of detection in the first preset time period, turn on the detection heavy pump light for atomic state pumping in the second preset time period, and turn on the detection light for the second step of detection in the third preset time period.

[0067] The atomic transition detection system in the cold atom microwave clock provided in this embodiment is used to implement the atomic transition detection method in the cold atom microwave clock provided in Embodiment 1, and has the same technical features as the atomic transition detection method in the cold atom microwave clock provided in Embodiment 1, so it can also solve the same technical problems and achieve the same technical effects.

[0068] Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working processes of the above-described systems, devices, and units can refer to the corresponding processes in the foregoing method embodiments, and will not be elaborated herein.

[0069] Embodiment 3

[0070] This embodiment also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the method described in any embodiment of the present application is implemented. The method is included in the above function descriptions and will not be elaborated here.

[0071] For example, it includes: one or more processors; a storage device for storing one or more programs. When the one or more programs are run by the one or more processors, the one or more processors implement the method provided in the embodiments of the present application. The method is included in the above function descriptions and will not be elaborated here.

[0072] The electronic device further includes an input device and an output device; the processor, storage device, input device, and output device in the electronic device can be connected via a bus or other means.

[0073] Embodiment Four

[0074] The present application provides a computer storage medium, on which a computer program is stored. When the program is executed by a processor, the steps of the method for detecting atomic transitions in a cold atom microwave clock in any of Embodiment One are implemented.

[0075] It can be understood that the storage medium includes: flash memory, hard disk, multimedia card, card-type memory (such as SD (Secure Digital Memory Card) or MDR (Memory Data Register)), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), magnetic memory, magnetic disk, optical disk, server, APP (Application) application mall, and other various media that can store program verification codes.

[0076] Embodiment Five

[0077] This embodiment provides a computer program product, including a computer program or instruction. When the computer program or instruction is executed by a processor, the method for detecting atomic transitions in a cold atom microwave clock described in Embodiment One is implemented.

[0078] Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a computer program product.

[0079] In several embodiments provided by this application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. The embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For another example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or direct coupling or communication connection between each other can be through some communication interfaces. The indirect coupling or communication connection of the devices or units can be in an electrical, mechanical, or other form.

[0080] The units described as separate components may or may not be physically separated. The components shown as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0081] In addition, in each embodiment of this application, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit.

[0082] It should be noted that the flowcharts and block diagrams in the accompanying drawings show the possible architectures, functions, and operations of systems, methods, and computer program products according to multiple embodiments of this application. In this regard, each block in the flowchart or block diagram can represent a module, a program segment, or a part of code, and the module, program segment, or part of code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order from that marked in the accompanying drawings. For example, two consecutive blocks can actually be executed substantially in parallel, and they can sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and the combination of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system for performing the specified functions or actions, or can be implemented by a combination of dedicated hardware and computer instructions.

[0083] Finally, it should be noted that the above-described embodiments are only specific embodiments of the present application, used to illustrate the technical solutions of the present application, rather than limiting it. The protection scope of the present application is not limited thereto. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that any person skilled in the art within the technical scope disclosed by the present application can still modify the technical solutions described in the foregoing embodiments or can easily think of changes, or perform equivalent replacements on some of the technical features; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

[0084] The applicant of the present application has made a detailed description and illustration of the embodiments of the present application in combination with the accompanying drawings of the specification. However, those skilled in the art should understand that the above embodiments are only the preferred implementation schemes of the present application, and the detailed description is only to help readers better understand the spirit of the present application, rather than a limitation on the protection scope of the present application. On the contrary, any improvement or modification made based on the inventive spirit of the present application should fall within the protection scope of the present application.

Claims

1. A method for detecting atomic transitions in a cold atom microwave clock, characterized in that including: Time-sharing measurement of the upper energy state signal of atoms in a cold atomic microwave clock using a single photodetector 1 and lower energy state signals 2; According to the upper energy state signal 1 and the lower energy state signal 2, the atomic transition probability is obtained .

2. The method for detecting atomic transition in a cold atom microwave clock according to claim 1, wherein The method uses a single photodetector to time-share the upper energy state signal of atoms in a cold atomic microwave clock. 1 and lower energy state signals 2, including: Turn on the probe light and turn it off after a first preset time period. Measure the upper energy state signal of the atoms in the cold atom microwave clock using a single photodetector within the first preset time period 1; Turn on the detection re-pump light and turn it off after a second preset time period to pump the atoms in the lower energy state to the upper energy state; Turn on the probe light and turn it off after a third preset time period. Measure the lower energy state signal of the atoms in the cold atom microwave clock using a single photodetector within the third preset time period 2.

3. The method for detecting atomic transitions in a cold atom microwave clock according to claim 1, characterized in that The atomic transition probability is obtained according to the upper energy state signal 1 and the lower energy state signal 2, and the following calculation formula is adopted: Among them, is the first constant coefficient, is the second constant coefficient.

4. An atomic transition detection system in a cold atom microwave clock, which is used to implement the atomic transition detection method in the cold atom microwave clock according to any one of claims 1 to 3, and is characterized in that, including: An atomic fluorescence acquisition device for collecting the fluorescence emitted when cold atoms are detected by a detection beam and outputting an electrical signal; A signal analysis module, configured to separate the electrical signal output by the atomic fluorescence acquisition device into an upper energy state signal 1 and a lower energy state signal 2; Transition probability calculation module, which is used to calculate the transition probability according to the upper energy state signal 1 and the lower energy state signal 2 .

5. The atomic transition detection system in the cold atom microwave clock according to claim 4, characterized in that, further including: A timing control module for turning on the detection light for the first step of detection in a first preset time period, turning on the detection re-pump light for atomic state pumping in a second preset time period, and turning on the detection light for the second step of detection in a third preset time period.

6. The atomic transition detection system in the cold atom microwave clock according to claim 4, wherein The atomic fluorescence acquisition device is composed of a lens in the center, a single photodetector respectively arranged on both sides of the lens, and a cold atom cloud movement area; where the cold atom cloud movement area is also the beam position of the detection light and the detection re-pump light.

7. An electronic device, characterized in that, including a memory, a processor, and a computer program stored on the memory and executable on the processor, the processor implementing the steps of the method for detecting atomic transitions in a cold atom microwave clock as described in any one of claims 1 to 3 when executing the computer program.

8. A computer storage medium, on which a computer program is stored, characterized in that, When the program is executed by the processor, it implements the steps of the method for detecting atomic transitions in a cold atom microwave clock as described in any one of claims 1 to 3.

9. A computer program product, comprising a computer program or instructions, characterized in that, When the computer program or instruction is executed by the processor, it implements the steps of the method for detecting atomic transitions in a cold atom microwave clock as described in any one of claims 1 to 3.

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